Music Store Question

Ok, about a year ago I authorized some school computers to play songs from my music store, but the problem is I don't remember which computers I authorized so I could deauthorize it. Is there anyway I can't just deauthorize all computers from my laptop, or will I have to figure out which ones they were?

MacRumors attracts a broad audience
of both consumers and professionals interested in
the latest technologies and products. We also boast an active community focused on
purchasing decisions and technical aspects of the iPhone, iPod, iPad, and Mac platforms.